Myositis ossificans in recurrent synovial hemangioma of the knee

: A case of myositis ossificans in 15-year old boy that occurred as a complication of the recurrent synovia hemangioma of the left knee was presented. The alteration was diagnosed as: osteosarcoma, chondrosarcoma and chondromyxoid fibroma by the pathologists from other institutions. The diagnosis of myositis ossificans was established using numerous histochemical and immunochemical methods (PAS, PAS diastasis, Alcian blue, Masson trichrom, von Kossa, Azur A, Toluidin blue, Goldner, method by Peris, Citokeratin, S-100, NSE and Vimentin). The presence of zonal phenomenon, as the one observed in the presented case, is one of the most significant criteria for differentiation of myositis ossificans from osteosarcoma.